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Structural analysis of Thermus thermophilus HB27 mannosyl-3-phosphoglycerate synthase provides evidence for a second catalytic metal ion and new insight into the retaining mechanism of glycosyltransferases

DOI: 10.1074/jbc.M109.095976 DOI Help
PMID: 20356840 PMID Help

Authors: Susana Goncalves (Instituto Tecnologia Quimica e Biologica) , Nuno Borges (Instituto Tecnologia Quimica e Biologica) , Ana Esteves (Instituto Tecnologia Quimica e Biologica) , Bruno Victor (Instituto Tecnologia Quimica e Biologica) , Claudio Soares (Instituto Tecnologia Quimica e Biologica) , Helena Santos (Instituto Tecnologia Quimica e Biologica) , Pedro Matias (Instituto Tecnologia Quimica e Biologica)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: March 2010
Diamond Proposal Number(s): 942

Abstract: Mannosyl-3-phosphoglycerate synthase is a glycosyltransferase involved in the two-step synthetic pathway of mannosylglycerate, a compatible solute that accumulates in response to salt and/or heat stresses in many microorganisms thriving in hot environments. The three-dimensional structure of mannosyl-3-phosphoglycerate synthase from Thermus thermophilus HB27 in its binary complex form, with GDP-?-d-mannose and Mg2+, shows a second metal binding site, about 6 Å away from the mannose moiety. Kinetic and mutagenesis studies have shown that this metal site plays a role in catalysis. Additionally, Asp167 in the DXD motif is found within van der Waals contact distance of the C1? atom in the mannopyranose ring, suggesting its action as a catalytic nucleophile, either in the formation of a glycosyl-enzyme intermediate according to the double-displacement SN2 reaction mechanism or in the stabilization of the oxocarbenium ion-like intermediate according to the DN*ANss (SNi-like) reaction mechanism. We propose that either mechanism may occur in retaining glycosyltransferases with a GT-A fold, and, based on the gathered structural information, we identified an extended structural signature toward a common scaffold between the inverting and retaining glycosyltransferases.

Journal Keywords: Catalytic; Crystallography; X-Ray; Glycosyltransferases; Ions; Kinetics; Mannose; Mannosyltransferases; Metals; Models; Biological; Models; Chemical; Models; Molecular; Mutagenesis; Thermus thermophilus

Subject Areas: Biology and Bio-materials

Instruments: I03-Macromolecular Crystallography